Braking systems are used in the automotive field, for example, to decelerate a motor vehicle in a controlled manner. For this purpose, a brake pedal force is usually converted into a brake pressure, which is transmitted with the aid of a brake medium to wheel cylinders of the motor vehicle in order to actuate same.
A vehicle braking system is described in German Published Patent Application No. 10 2008 012 874. The vehicle braking system includes hydraulically actuatable wheel brake cylinders and a pressure supply system for acting on the wheel brakes with a brake pressure. When a driver of the motor vehicle actuates the vehicle braking system, the intensity of the driver braking input is ascertained. The volume of an expanding device is changed as a function of the ascertained driver braking input. The pressure supply system couples a brake pedal for transmitting the driver input and a brake booster to wheel brake cylinders of the vehicle. When the brake pedal is actuated, a master brake cylinder together with pistons of the pressure supply system, which is connected to the wheel brake cylinders via two brake circuits, is indirectly actuated. In addition, the brake booster includes an electric motor via which an assisting, i.e., additional, force is indirectly applied to the piston of the master brake cylinder. Since the piston of the master brake cylinder has a defined surface area, and is also coupled to the piston of the master brake cylinder in a defined manner, the position of the piston of the master brake cylinder may be deduced from the angular position of a drive shaft of the electric motor. The displaced volume of brake medium from the master brake cylinder may be ascertained based on this position.